1. Field of the Invention
The present invention relates generally to applicator guns that are often used for dispensing two-part materials and, more particularly, to an applicator gun with straight-through flow paths or lumens.
2. Description of Related Art
FIGS. 1 to 3 show a prior art applicator gun 10 sold by applicant's company under the X-GUN® brand, model X2002A. It features a dual rack-and-pinion gear system 60/70 that is driven by a trigger-operated air cylinder. The illustrated applicator gun 10 is often used for dispensing two-part materials A&B, consisting for example of a resin (A) and a hardener (aka catalyst) (B).
In broad strokes, the applicator gun 10 comprises a trigger assembly 30, a cylinder assembly 40, a fluid section assembly 50, and a tip assembly 90. In a bit more detail, the trigger assembly includes a handle 21 with a trigger 20 and a trigger body 31; the cylinder assembly 40 includes a cylinder body 41, a piston 42, and a rod 43; and the fluid section assembly 50 includes a valve body 51 with right-angle lumens and a pair of right-angle fittings 11a, 11b. 
In FIG. 1, the applicator gun's tip assembly 90 is equipped with a simple two-port tip 91. In use, this tip 91 is used with a “static mixer” which generally comprises an elongated tube or tube assembly having a flared proximal end and internal features that mix the fluids prior to exiting. The flared end of the static mixer is connected to tip 91 with a nut that engages the threads of the tip 91 and then, when the applicator gun 10 is operated, the A and B materials flow out of the tip 91 and into the static mixer. In this embodiment, the applicator gun 10 might be used to apply a thick bead of epoxy adhesive for assembling one component to another large component.
The tip assembly 90 may have an different construction and manner of operation in other embodiments. For example, the applicator gun 10 may be used for different purposes, e.g. for application of a lower viscosity gelcoat in which case the tip assembly may comprising air fittings, apertured plates, etc, for atomizing the A- and/or B-materials just prior to mixing and/or after exiting the tip assembly 90.
The applicator gun 10 may also be used for numerous other purposes, e.g. application of higher viscosity granite spray, etc., in which case the tip assembly would be purpose-built for that function. The exact design of the tip assembly may vary from embodiment to embodiment. Common to all embodiments, however, is the need for an applicator gun 10 that delivers the A- and B-materials with an applicator gun 10 that is as compact as possible for maneuvering. Also, for purposes of reducing fatigue by those who must use the applicator gun for hours on end, it needs to be as light as possible and the operation of the trigger should require as little pressure as possible to initiate and maintain the A- and B-flows.
As best shown in FIG. 1, the A and B materials enter the applicator gun 10 through the two right-angle fittings 11a and 11 b that lead into the side of the valve body 51, through two more right-angle turns 12a, 12b inside of the valve body 51, and finally exit the valve body 51 at output apertures 13a,13b. As best shown in FIG. 3, the right-angle fittings 11a, 11b were necessary to provide A- and B-attachment points in relatively wide locations on either side of the cylinder body 41.
In operation, the user pulls on the trigger 20 to control the trigger body 31 that passes high pressure shop air to the cylinder body 41 to operate an air actuated piston 42 in the cylinder body 41 that in turn operates a rod 43 that opens and closes a valve mechanism 60/70/80 in the valve body 51. As shown, the dual rack and pinion mechanism 60/70 is comprised of a two-sided rack 60, a pair of pinions 70, 70. The pinions 70 rotate corresponding ball valves 80, 80. FIG. 1 only shows one pinion 70, one ball valve 80, and associated components for the sake of simplicity, but the other side is identical.
In operation, the gear rack 60 is driven back and forth by the rod 43 to rotate the pinions 70, 70 that, via corresponding shafts 72, 72, rotate and thereby open the two ball valves 80, 80 by aligning their through-holes 81 with the flow paths leading to the output apertures 13a, 13b which, in turn, let the A & B chemicals pass through and exit the tip assembly 90 of the gun. Releasing the trigger 20 closes the ball valves 80, 80 and stops the flow of the A & B materials.
FIG. 2 is a close-up view of the rack and pinion mechanism 60/70 on the underside of the gun's upper assembly. As shown, the A and B flow is from left to right, and each flow path includes a pair of right-angle turns (i.e. 11a, 12a and 11 b, 12b).
FIG. 3 is a perspective view of the prior art applicator gun 10 showing the multi-turn flow path associated with its A-side flow in heavy dashed lines, the B-side being a mirror image
The prior art model X2002A gun 10 and its rotating ball valves 80, 80, driven open and held open by an air piston 32 whenever the user lightly pulled the trigger 20, provided significant durability and ease-of-operation benefits relative to other applicator guns that used conventional needle valves that were manually opened against a spring force and maintained in that state by the user's grip alone. The X2002A, moreover, eliminated the need to use troublesome needle valves and related seats and, in particular, featured ball valves 80, 80 that are fully open when opened, whereas the needle valves inherently left a narrow, tapered part of the needle in the flow path.
The model X2002A gun 10 offered valve-related flow advantages, but it still exhibited some flow-related shortcomings in certain more-demanding applications. For example, when relatively bulky, crushed materials are mixed with the resin to replicate the appearance of granite countertops (e.g. GRANICOAT® or other sprayable granite coatings and coring materials), the crushed materials may occasionally get trapped in the non-straight A & B flow paths—see the right-angle fittings and right-angle flow paths through the central valve body 50 of FIGS. 1 and 2 (i.e. 11a, 12a and 11b, 12b).
Because of the right-angle flow paths, with two bends on each side, higher than ideal pump pressures were also required to move the relatively bulky materials through the gun, even if flow continued without material becoming trapped. Finally, because of the associate back pressure, the right-angle flow paths would inherently exaggerate the magnitude of the so-called “wink,” i.e. the periodic drop in pressure and corresponding drop in spray volume associated with pump transitions.
There remains a need, therefore, for an improved applicator gun with straight-through flow paths.